The present invention relates to a new and improved method of, and apparatus for, manufacturing a light construction element, particularly a cover plate.
The present invention relates specifically to a new and improved method of, and apparatus for, manufacturing a light construction element, particularly a cover plate, in which a blank comprising an upper layer of an expandable first clay material and a lower layer of a second clay material which is incapable of expanding at least in the range of the expansion temperature of the first clay material is fired in an oven such that the first clay material expands and is sintered to the second clay material at the interconnecting surface.
The initially mentioned subjects are known as, for example, from British Patent No. 1,279,980 and German Patent Publication No. 1,933,421, respectively. In the procedure as described therein, for instance, a layer of an expandable first clay material is arranged on a layer consisting of a second clay material which is not capable of expansion at the swelling temperature of the first clay material. There the layer of the second clay material is introduced into a mold and, then, the first clay material is deposited thereupon in the form of particles or pieces. Such method, however, did not render useful results since, on the one hand, a large surface is formed which oxidizes on firing and, thereby, prevents swelling due to the cavities intermediate the particles and, on the other hand, due to the cavities the heat transfer is too poor to ensure sufficient and particularly uniform swelling. Due to the cavities the further described radiation heating cannot become sufficiently effective, particularly, since the side walls of the mold also have a cooling action.